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Physicists tweak quantum force, reducing barrier to tiny devices
Posted on Monday, July 14, 2008 @ 23:13:56 UTC by vlad
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 A scanning electron micrograph, taken with an electron microscope,
shows the comb-like structure of a metal plate at the center of newly
published University of Florida research on quantum physics. UF
physicists found that corrugating the plate reduced the Casimir force,
a quantum force that draws together very close objects. The discovery
could prove useful as tiny "microelectromechanical" systems --
so-called MEMS devices that are already used in a wide array of
consumer products -- become so small they are affected by quantum
forces. Credit: Yiliang Bao and Jie Zoue/University of Florida
Cymbals don't clash of their own accord – in our world, anyway. But the
quantum world is bizarrely different. Two metal plates, placed almost
infinitesimally close together, spontaneously attract each other.
What seems like magic is known
as the Casimir force, and it has been well-documented in experiments.
The cause goes to the heart of quantum physics: Seemingly empty space
is not actually empty but contains virtual particles associated with
fluctuating electromagnetic fields. These particles push the plates
from both the inside and the outside. However, only virtual particles
of shorter wavelengths — in the quantum world, particles exist
simultaneously as waves — can fit into the space between the plates, so
that the outward pressure is slightly smaller than the inward pressure.
The result is the plates are forced together.
Now, University of Florida
physicists have found they can reduce the Casimir force by altering the
surface of the plates. The discovery could prove useful as tiny
"microelectromechanical" systems — so-called MEMS devices that are
already used in a wide array of consumer products — become so small
they are affected by quantum forces.
"We are not talking about an immediate application," says Ho Bun
Chan, an assistant professor of physics and the first author of a paper
on the findings that appears today in the online edition of the journal
Physical Review Letters.
"We are talking about, if the
devices continue to be smaller and smaller, as the trend of
miniaturization occurs, then the quantum effects could come into play."
More specifically, the finding could one day help reduce what MEMS
engineers call "stiction" — when two very small, very close objects
tend to stick together.
Although stiction has many causes — including, for example, the
presence of water molecules that tend to clump together — the Casimir
force can contribute. Such quantum effects could prove important as the
separations between components in tiny machinery shrink from
micrometer, or millionths of a meter, toward nanometer size, Chan said.
"A lot of people are thinking of ways to reduce stiction, and this research opens up one possibility," he said.
Dutch physicist Hendrik Casimir first predicted that two closely
spaced metal plates would be mutually attracted in 1948. It took
several decades, but in 1996, physicist Steve Lamoreaux, then at the
University of Washington, performed the first accurate measurement of
the Casimir force using a torsional pendulum, an instrument for
measuring very weak forces.
Subsequently, in a paper published in Science in 2001, Chan and
other members of a Bell Labs team reported tapping the Casimir force to
move a tiny metal see-saw. The researchers suspended a metal sphere an
extremely tiny but well-controlled distance above the see-saw to "push"
it up and down. It was the first demonstration of the Casimir force
affecting a micromechanical device.
In the latest research, the physicists radically altered the shape
of the metal plates, corrugating them into evenly spaced trenches so
that they resembled a kind of three-dimensional comb. They then
compared the Casimir forces generated by these corrugated objects with
those generated by standard plates, all also against a metal sphere.
The result? "The force is smaller for the corrugated object but not
as small as we anticipated," Chan said, adding that if corrugating the
metal reduced its total area by half, the Casimir force was reduced by
only 30 to 40 percent.
Chan said the experiment shows that it is not possible to simply
add the force on the constituent solid parts of the plate — in this
case, the tines — to arrive at the total force. Rather, he said, "the
force actually depends on the geometry of the object."
"Until now, no significant or nontrivial corrections to the Casimir
force due to boundary conditions have been observed experimentally,"
wrote Lamoreaux, now at Yale University, in a commentary accompanying
publication of the paper.
Source: University of Florida
Via: http://www.physorg.com/news135257349.html
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Re: Physicists tweak quantum force, reducing barrier to tiny devices (Score: 1)
by ElectroDynaCat on Tuesday, July 15, 2008 @ 10:44:50 UTC
(User Info | Send a Message) | Its reassuring to see that some serious research is going on instead of the nonsense we usually see posted about fantastic claims.
I might add to Mr. Chans' statement about the "force actually depends on the geometry", it also is dependent on the size.
Scaling laws tell us that as volume decreases as the 3rd power of scale, surface area only decreases as the 2nd power of scale.
Vacuum flux forces are dependent on surface area, not volume. |
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